Light emitting diode and method for manufacturing the same

ABSTRACT

A light emitting diode includes a first electrode, a second electrode and an epitaxial structure. The epitaxial structure is arranged on the first electrode, and electrically connects with the first electrode and the second electrode. The second electrode surrounds periphery of the epitaxial structure to reflect light from the epitaxial structure to emit out from the top of the epitaxial structure. This disclosure also relates to a method for manufacturing the light emitting diode. The light emitting diode and the method help solve the problem of low light efficiency of the light emitting diode.

FIELD

The subject matter relates to semiconductor structures, and particularlyrelates to a light emitting diode and manufacturing method thereof.

BACKGROUND

A traditional light emitting diode includes a light transmissionsubstrate, an N-type semiconductor layer, an active layer, a P-typesemiconductor layer, a P-type electrode and an N-type electrode. TheP-type electrode is arranged on a surface of the P-type semiconductorlayer and the N-type electrode is arranged on a surface of the N-typesemiconductor layer. Part of light emitted from the active layer isreflected by the N-type electrode and the P-type electrode, which willreduce light efficiency thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures:

FIG. 1 is a cross-section view of a light emitting diode in accordancewith a first exemplary embodiment of the present disclosure.

FIG. 2 is a cross-section view of a light emitting diode in accordancewith a second exemplary embodiment of the present disclosure.

FIGS. 3-15 are cross-sectional views showing semi-finished lightemitting diodes processed by different steps of a method formanufacturing an light emitting diode accordance with an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale and the proportions of certain parts havebeen exaggerated to better illustrate details and features of thepresent disclosure.

FIG. 1 shows a light emitting diode 100 of a first embodiment in thepresent disclosure.

Referring to FIG. 1, the light emitting diode 100 in the firstembodiment includes a first electrode 10, a second electrode 20 and anepitaxial structure 30. The epitaxial structure 30 is arranged on thefirst electrode 10. The epitaxial structure 30 is electrically connectedto the first electrode 10 and the second electrode 20 respectively. Thesecond electrode 20 surrounds periphery of the epitaxial structure 30and materials with reflecting property can be coated on inner surfacesof the second electrode 20 to reflect light emitted from the epitaxialstructure 30 to emit out from top of the epitaxial structure 30.

The first electrode 10 includes a top surface 11, a bottom surface 12opposite to the top surface 11 and side surfaces 13. Each side surface13 connects the top surface 11 to the bottom surface 12. The firstelectrode 10 has a reflecting property to reflect light. Preferably, thefirst electrode 10 is made of Cr or Au or materials with reflectingproperty are coated on the top surface 11 of the first electrode 10.

The epitaxial structure 30 is arranged on the top surface 11 of thefirst electrode 10. A diameter of the epitaxial structure 30 is largerthan the diameter of the first electrode 10. The bottom of the epitaxialstructure 30 is directly attached on the top surface 11 of the firstelectrode 10 to be electrically connected to the first electrode 10. Theperiphery of the epitaxial structure 30 extends over the side surfaces13 of the first electrode 10. A vertical cross-section of the firstelectrode 10 and the epitaxial structure 30 is shaped as a letter T.

The epitaxial structure 30 includes a first semiconductor layer 31, anactive layer 32 and a second semiconductor layer 33. The firstsemiconductor layer 31, the active layer 32 and the second semiconductorlayer 33 are arranged on the first electrode 10 that order. The firstsemiconductor layer 31 is directly attached on the top surface 11 of thefirst electrode 10 to electrically connect the epitaxial structure 30 tothe first electrode 10. In this exemplary embodiment, the firstsemiconductor layer 31 is a P—GaN layer, the active layer 32 is amultiple quantum wells (MQWs) layer, and the second semiconductor layer33 is an N—GaN layer.

The second electrode 20 includes a base 21 and an extension 22. Theextension 22 extends upwardly from the top of the base 21. In thisexemplary embodiment, the first electrode 10 is surrounded by the base21, and the periphery of the epitaxial structure 30 is surrounded by theextension 22.

A width of the base 21 is greater than the width of the extension 22. Inthis exemplary embodiment, the extension 22 remains an identical height.A thickness of the base 21 is almost the same as the thickness of thefirst electrode 10. Preferably, the top surface of the base 21 and thetop surface 11 of the electrode 10 are coplanar, and the bottom surfaceof the base 21 and the bottom surface 12 of the electrode 10 arecoplanar.

The base 21 and the first electrode 10 are spaced apart from each other,and a first annular groove 40 is defined therebetween. Preferably, thefirst annular groove 40 is filled with an insulating layer 41. Theinsulating layer 41 can be SiO₂, SiN_(x) or SU-8 resin. Preferably, theinsulating layer 41 is SiO₂. Materials with reflecting property arecoated on surfaces of the insulating layer 41 to reflect light.

The extension 22 extends upwardly along the periphery of the epitaxialstructure 30. The whole periphery of the epitaxial structure 30 issurrounded by the extension 22. A bottom inner edge 221 of the extended22 is spaced apart from the first semiconductor layer 31 and the activelayer 32, therewith a second annular groove 50 defined. The secondannular groove 50 is surrounded by the bottom inner edge 221 of theextension 22, a peripheral lateral surface 311 of the firstsemiconductor layer 31 and a peripheral lateral surface 321 of theactive layer 32. Preferably, the second annular groove 50 is filled withthe insulating layer 41.

The second annular groove 50 is defined between the top surface ofsecond electrode 20 and the bottom surface of the second semiconductorlayer 33. Preferably, a depth D of the second annular groove 50 is equalto a sum of depths of the first semiconductor layer 31 and the activelayer 32. In other exemplary embodiments, the depth D of the secondannular groove 50 can be larger than the sum of depths of the firstsemiconductor layer 31 and the active layer 33, but smaller than aheight H of the epitaxial structure 30.

The top inner edge 222 of the extension 22 directly contacts the secondsemiconductor layer 33 to electrically connect the second electrode 20to the epitaxial structure 30. Preferably, a height of the extension 22extending upwardly from the top of the base 21 is equal to the height Hof the epitaxial structure 30, therewith the top surface of theextension 22 and an outside surface 331 of the second semiconductorlayer 33 being coplanar. In this exemplary embodiment, the outsidesurface 331 of the second semiconductor layer 33 is a top emittingsurface of the light emitting diode 100.

Because the first electrode 10 of the light emitting diode 100 in thepresent disclosure is located at the bottom of the epitaxial structure30 and the periphery of the epitaxial structure 30 is surrounded by thesecond electrode 20, medial light emitted from the epitaxial structure30 emits out from top of the epitaxial structure 30 directly, and sidelight emitted from the epitaxial structure 30 is reflected by the secondelectrode 20 to emit out from top of the epitaxial structure 30, therebybetter light efficiency of the light emitting diode 100 obtained.

Additionally, the first annular groove 40 and the second annular groove50 are respectively filled with the insulating layers 41. Light emittingto the bottom of the epitaxial structure 30 is reflected by theinsulating layers 41 to emit out from top of the epitaxial structure 30.So the light is prevented from being emitted out from the second annulargroove 50, but is allowed to be emitted out from the top of theepitaxial structure 30, thereby improving light efficiency.

The light emitting diode 100 can also include a light transmission layer60. In this exemplary embodiment, the light transmission layer 60 isconfigured on top of the extension 22 and the outside surface 331 of thesecond semiconductor layer 33. The light transmission layer 60 coversthe top of the extension 22 and the outside surface 331 of the secondsemiconductor layer 33. The light transmission layer 60 is made ofmaterials with good light transmission properties. The lighttransmission layer 60 can protect the epitaxial structure 30 frommoisture and dust and enhance mechanical strength. In this exemplaryembodiment, the light transmission layer 60 can be a sapphire substrate.

The light emitting diode 100 can further include a protective layer 70.The protective layer 70 is extended from the top surface of the base 21and along the periphery of the extension 22 of the second electrode 20.The protective layer 70 encloses the extension 22 and the lighttransmission layer 60.

The protective layer 70 is made of materials with good thermalconductivity and good light transmission properties. The protectivelayer 70 protects the light transmission layer 60 and the extension 22of the second electrode 20 and enhances mechanical strength of the wholelight emitting diode 100. Heat generated from the epitaxial structure 30can be transferred by the extension 22 of the second electrode 20 to theprotective layer 70. So the protective layer 70 also has a goodadvantage in dissipating heat.

FIG. 2 shows a light emitting diode 200 of a second embodiment in thepresent disclosure.

Referring to FIG. 2, compared with the light emitting diode 100 of thefirst embodiment, a difference therebetween is that the epitaxialstructure 30 of the light emitting diode 200 of the second embodimentfurther includes a buffer layer 34. The buffer layer 34 is formedbetween the light transmission layer 60 and the second semiconductorlayer 33. The buffer layer 34 further includes a cryo unalloyed GaNlayer 341 and a pyro unalloyed GaN layer 342. The pyro unalloyed GaNlayer 342 and the cryo unalloyed GaN layer 341 are configured on thesecond semiconductor layer 33 that order.

A method for manufacturing a light emitting diode is also provided inthe present disclosure.

Referring from FIG. 3 to FIG. 15, the method for manufacturing the lightemitting diode includes:

growing an epitaxial layer 20 b on a light transmission substrate 10 b;the epitaxial layer 20 b comprising at least a first semiconductor layer21 b, an active layer 22 b and a second semiconductor layer 23 b thatorder from the top down;

defining a plurality of annular pits 301 b on the epitaxial layer 20 b;each annular pit 301 b penetrating through at least the firstsemiconductor layer 21 b and the active layer 22 b;

filling each annular pit 301 b with a corresponding insulating layer 40b;

forming a plurality of individual epitaxial structures 100 b by etchingparts of the epitaxial layer 20 b surrounding periphery of the annularpits 301 b; the epitaxial structures 100 b being spaced apart from eachother and a corresponding channel 50 b being defined therebetween;

forming a plurality of conductive layers 60 b in the channels 50 b to bethe second electrode 400 b; each conductive layer 60 b coveringperiphery of a corresponding epitaxial structure 100 b;

dividing the light transmission substrate 10 b to form a plurality ofseparate epitaxial structures 100 b;

forming a first electrode 300 b to form a light emitting diode 500.

Referring to FIG. 3, an epitaxial layer 20 b is grown on a lighttransmission substrate 10 b. The epitaxial layer 20 b includes at leasta first semiconductor layer 21 b, an active layer 22 b and a secondsemiconductor layer 23 b that order from the top down. In this exemplaryembodiment, the epitaxial layer 20 b can further include a buffer layer24 b. The buffer layer 24 b is configured between the light transmissionsubstrate 10 b and the second semiconductor layer 23 b to raise thegrown quantity of the epitaxial layer 20 b. Preferably, the buffer layer24 b includes a cryo unalloyed GaN layer 241 b and a pyro unalloyed GaNlayer 242 b. The cryo unalloyed GaN layer 241 b is grown on the lighttransmission substrate 10 b and the pyro unalloyed GaN layer 242 b isgrown on the cryo unalloyed GaN layer 241 b. In this exemplaryembodiment, the first semiconductor layer 21 b is a P—GaN layer, theactive layer 22 b is a multiple quantum wells (MQWs) layer, and thesecond semiconductor layer 23 b is an N—GaN layer.

Referring from FIG. 4 to FIG. 6, a plurality of annular pits 301 b aredefined on the epitaxial layer 20 b. Each annular pit 301 b penetratesin at least the first semiconductor layer 21 b and the active layer 22b.

Preferably, forming the annular pits 301 b includes:

A photoresist layer 30 b is formed on the epitaxial layer 20 b. Severalthrough holes 300 b are defined on the photoresist layer 30 b. Thethrough holes 300 b are spaced apart from each other. In this exemplaryembodiment, each through hole 300 b is ring-shaped. Part surface of thefirst semiconductor layer 21 b of the epitaxial layer 20 b is exposed bythe through holes 300 b. The photoresist layer 30 b is negativephotoresist. The photoresist layer 30 b can be made of polyisoprene.

The epitaxial layer 20 b is etched downward along the through holes 300b to form the annular pits 301 b. Each annular pit 301 b connects to acorresponding through hole 300 b. Each annular pit 301 b is extendeddownward in height direction of the epitaxial layer 20 b. Each annularpit 301 b penetrates through the photoresist layer 30 b, the firstsemiconductor layer 21 b and the active layer 22 b to expose the secondsemiconductor layer 23 b.

Referring to FIG. 7, each annular pit 301 b is filled with acorresponding insulating layer 40 b. Preferably, the insulating layer 40b is introduced as SiO₂.

Referring from FIG. 8 to FIG. 10, a plurality of epitaxial structures100 b are formed by etching parts of the epitaxial layer 20 bsurrounding periphery of the annular pits 301 b. The epitaxialstructures 100 b are spaced apart from each other and a correspondingchannel 50 b is defined therebetween.

Preferably, forming the channels 50 b includes:

Referring to FIG. 8, the photoresist layer 30 b is removed.

Referring to FIG. 9, a plurality of new photoresist layers 30 b areformed on the epitaxial structures 100 b. Each photoresist layer 30 bcovers a corresponding insulating layer 40 b and parts of the epitaxiallayer 20 b surrounded by the corresponding insulating layer 40 b. Acorresponding spacer region 320 b is defined between two adjacentphotoresist layers 30 b. In this exemplary embodiment, each spacerregion 320 b is ring-shaped.

Referring to FIG. 10, the epitaxial structures 100 b are formed byetching the epitaxial layer 20 b downward along the spacer regions 320b. Each channel 50 b is defined between two adjacent epitaxialstructures 100 b. Each channel 50 b is ring-shaped.

In this exemplary embodiment, each channel 50 b penetrates through thefirst semiconductor layer 21 b, the active layer 22 b, the secondsemiconductor layer 23 b and the buffer layer 24 b to bottom of thechannels 50 b.

Referring from FIG. 11 to FIG. 12, a plurality of conductive layers 60 bare formed in the channels 50 b. Each conductive layer 60 b coversperiphery of a corresponding epitaxial structure 100 b.

Preferably, forming the conductive layers 60 b includes:

Referring to FIG. 11, a plurality of photoresist layers 30 c are formedin the channels 50 b. Each epitaxial structure 100 b is surrounded by acorresponding photoresist layer 30 c. Each photoresist layer 30 c isspaced apart from a corresponding epitaxial structure 100 b. Preferably,a height of the photoresist layer 30 c is equal to that of thecorresponding epitaxial structure 100 b. In this exemplary embodiment,material composing the photoresist layers 30 c is the same with materialcomposing the photoresist layers 30 b.

Referring to FIG. 12, each conductive layer 60 b is formed between thecorresponding photoresist layer 30 c and periphery of the correspondingepitaxial structure 100 b. Each conductive layer 60 b covers theperiphery of the corresponding epitaxial structures 100 b and peripheryof a corresponding insulating layer 40 b. Preferably, a height of eachconductive layer 60 b is equal to that of the corresponding epitaxialstructure 100 b.

Referring to FIG. 13 to FIG. 14, the light transmission substrate 10 bis divided to form a plurality of separate epitaxial structures 100.

Forming the separate epitaxial structures 100 includes:

Referring to FIG. 13, the photoresist layers 30 b and 30 c are removedto form a gap 70 b between two adjacent epitaxial structures 100.

Referring to FIG. 14, the epitaxial structures 100 are separated bycutting the light transmission substrate 10 b. In detail, the epitaxialstructures 100 are reversed and the light transmission substrate 10 bcan be cut along the gaps 70 b by laser light. In detail, the lighttransmission substrate 10 b is cut by laser light after the epitaxialstructures 100 being reversed and placed on a blue adhesive tape 200 b.

Referring to FIG. 15, a first electrode 300 b and a second electrode 400b are formed to form a light emitting diode 500.

Configuring the first electrode 300 b and the second electrode 400 bincludes:

A metal layer is configured under the first semiconductor layer 21 b toform the first electrode 300 b. In some embodiments, the conductivelayer 60 b can be the second electrode 400 b. In this exemplaryembodiment, another metal layer is configured under the conductive layer60 b. The metal layer and the conductive layer 60 b are coupled to bethe second electrode 400 b.

Preferably, an annular slot 350 b is formed between the first electrode300 b and the second electrode 400 b. The annular slot 350 can be filledwith the insulted layer 40 b. The insulted layer 40 b is introduced asSiO2.

The method for manufacturing the light emitting diode further mayinclude: forming a protective layer 70 (referring to FIG. 2). Theprotective layer 70 is located outside of the light emitting diode 500.The protective layer 70 encloses the light transmission substrate 10 band the conductive layer 60 b. The protective layer 70 is made ofmaterials with good thermal conductivity and good light transmissionproperties. Preferably, the protective layer 70 is made of AlN.

In the process of manufacturing the light emitting diode, because thesecond electrode 20/400 b surrounds the periphery of the epitaxialstructures 30/100 b, side light from the epitaxial structure 30/100 b isreflected by the second electrode 20/400 b to emit out from the top ofthe light emitting diode 100/200/500, thereby improving light efficiencyof the light emitting diode 100/200/500.

The embodiment shown and described above is only an example. Manydetails are often found in the art such as the other features of thelight emitting diode. Therefore, many such details are neither shown nordescribed. Even though numerous characteristics and advantages of thepresent technology have been set forth in the foregoing description,together with details of the structure and function of the presentdisclosure, the disclosure is illustrative only, and changes may be madein the detail, especially in matters of shape, size and arrangement ofthe parts within the principles of the present disclosure up to, andincluding the full extent established by the broad general meaning ofthe terms used in the claims. It will therefore be appreciated that theembodiments described above may be modified within the scope of theclaims.

What is claimed is:
 1. A light emitting diode, comprising: a firstelectrode, a second electrode, and an epitaxial structure arranged onthe first electrode and electrically connected to the first electrodeand the second electrode; wherein the second electrode surroundsperiphery of the epitaxial structure to reflect light emitted from theepitaxial structure to emit out from top of the epitaxial structure. 2.The light emitting diode of claim 1, wherein the epitaxial structurecomprises at least a first semiconductor layer, an active layer and asecond semiconductor layer arranged on the first electrode that order.3. The light emitting diode of claim 2, wherein the first semiconductorlayer directly contacts with and is electrically connected to the firstelectrode, and the second semiconductor layer is electrically connectedto the second electrode.
 4. The light emitting diode of claim 3, whereinthe second electrode comprises a base and an extension, and theextension extends upwardly from top surface of the base.
 5. The lightemitting diode of claim 4, wherein the first electrode is surrounded bythe base, and a first annular groove is defined between the base and thefirst electrode.
 6. The light emitting diode of claim 5, wherein thefirst annular groove is filled with insulating materials.
 7. The lightemitting diode of claim 4, wherein the epitaxial structure is surroundedby the extension, and the second semiconductor layer is directlycontacts with the extension of the second electrode.
 8. The lightemitting diode of claim 7, wherein a second annular groove is definedbetween a bottom inner edge of the extension, a peripheral lateralsurface of the first semiconductor layer and a peripheral lateralsurface of the active layer.
 9. The light emitting diode of claim 8,wherein the second annular groove is filled with insulating materials.10. The light emitting diode of claim 4, further comprising a lighttransmission layer, wherein the light transmission layer is formed ontop of the extension and an outside surface of the second semiconductorlayer.
 11. The light emitting diode of claim 10, further comprising aprotective layer, wherein the protective layer extends from top surfaceof the base and along periphery of the extension of the secondelectrode.
 12. The light emitting diode of claim 11, further comprisinga buffer layer, wherein the buffer layer is formed between the lighttransmission layer and the second semiconductor layer.
 13. A method formanufacturing a light emitting diode, comprising: growing an epitaxiallayer on a light transmission substrate; the epitaxial layer comprisingat least a first semiconductor layer, an active layer and a secondsemiconductor layer that order from the top down; defining a pluralityof annular pits on the epitaxial layer; each annular pit penetratingthrough at least the first semiconductor layer and the active layer;filling each annular pit with a corresponding insulating layer; forminga plurality of individual epitaxial structures by etching parts of theepitaxial layer surrounding periphery of the annular pits; the epitaxialstructures being spaced apart from each other and a correspondingchannel being formed therebetween; forming a plurality of conductivelayers in the channels to be the second electrode; each conductive layercovering periphery of a corresponding epitaxial structure; dividing thelight transmission substrate to form a plurality of separate epitaxialstructures; and forming a first electrode to form a light emittingdiode.
 14. The method for manufacturing a light emitting diode of claim13, wherein forming the annular pits comprising: forming a photoresistlayer on the epitaxial layer, a plurality of through holes being definedon the photoresist layer, each through hole being ring-shaped; andetching the epitaxial layer downward along the through holes to form theannular pits.
 15. The method for manufacturing a light emitting diode ofclaim 14, wherein the epitaxial layer is etched downward and penetratesthrough the first semiconductor layer and the active layer to expose thesecond semiconductor layer.
 16. The method for manufacturing a lightemitting diode of claim 14, wherein forming the channels comprising:removing the photoresist layer; forming a plurality of new photoresistlayers on the epitaxial structures; each new photoresist layer coveringa corresponding insulating layer and parts of the epitaxial layersurrounded by the corresponding insulating layer, a corresponding spacerregion being defined between the two adjacent new photoresist layers;and eaching the epitaxial layer downward along the spacer regions toform the epitaxial structures, each channel being defined between thetwo adjacent epitaxial structures, bottom of the channels being occludedby the light transmission substrate.
 17. The method for manufacturing alight emitting diode of claim 16, wherein forming the conductive layerscomprising: forming a plurality of photoresist layers in the channels,each epitaxial structure being surrounded by a corresponding photoresistlayer and each photoresist layer being spaced apart from a correspondingepitaxial structure; and forming the conductive layer between thecorresponding photoresist layer and periphery of the correspondingepitaxial structure; each conductive layer covering the periphery of thecorresponding epitaxial structures and periphery of a correspondinginsulating layer.
 18. The method for manufacturing a light emittingdiode of claim 17, wherein a height of each conductive layer is equal tothat of the corresponding epitaxial structure.
 19. The method formanufacturing a light emitting diode of claim 18, wherein forming theseparate epitaxial structures comprising: removing the photoresistlayers to form a gap between two adjacent epitaxial structures; andcutting the light transmission substrate along the gaps to form theseparate epitaxial structures.
 20. The method for manufacturing a lightemitting diode of claim 19, wherein the epitaxial structures is reversedbefore incised.